The present invention pertains generally to alloys and in particular to magnetic iron-boron alloys.
Iron alloys, including iron-boron alloys, have been used extensively as magnets, both soft and hard. A hard magnetic alloy is one with a high coercive force and remanence, whereas a soft magnetic alloy is one with a minimum coercive force and minimum area enclosed by the hysteresis curve. Examples of iron-boron alloys suitable as magnets are found in U.S. Pat. Nos. 4,134,779, 4,226,619; and 4,249,969.
Magnetic ferrous alloys with some members of the lanthanide series are known, for example, the alloys of U.S. Pat. No. 4,065,330. Two amorphous, iron-rare earth alloys are known to exhibit hard magnetic properties at room temperature. In A. E. Clark Applied Phys. Letter 23, 642 (1973), an amorphous TbFe.sub.2 alloy, produced by rapid sputtering, is reported to develop a coercive force of 3.4 kOe at room temperature. Amorphous Pr-Fe alloys, produced by melt spinning, have been shown in J. J. Croat Appl. Phys. Letter 37, 1096 (1980) to have coercive forces up to 2.8 kOe. Also, intermetallic compounds of iron and certain lanthanides have been used as magnetostrictive materials. Examples of these compounds are disclosed in Koon et al. Phys. Lett. 34A 5, p. 413 (1971). However, no iron-lanthanum alloys have been prepared because of the instability of the combination.
Alloying iron, boron, and a lanthanide to produce an alloy with a microstructure giving excellent magnetic or magnetostrictive properties has also not been successful. An amorphous microstructure is particularly appealing and has received a great deal of attention in recent years, mainly because of their potential for use in high-performance, low-loss transformers. The attractiveness of amorphous alloys for such application is due, in part, to the fact that a material that lacks a regular crystal structure cannot have conventional magnetic anisotropy. Because amorphous alloys combine low magnetic anisotropy with a very uniform microstructure, they are generally very easy to magnetize, often requiring only fractions of an Oersted to achieve almost complete saturation. Unfortunately attempts to produce amorphous iron-boron-lanthanide alloys have not been successful. Instead of obtaining an amorphous alloy, an intermetallic compound is obtained.